I World Population: Retrospect and Prospect Philip M. Hauser Woild population at the beginning of 1969 numbered^S-Mlion. About one and a half generations ago,.,juiJj930, it was 2 billion. About eleven or twelve generations ago, in J^SQrrthe onset of the modern era— it was only half a billion. In little more than one human generation hence, 2000, world popula-tiqriJiojild_-&as*fy^ In about two human generations from now, 2020, world population could approximate 10 billion; and in about four human generations, 2070, world population could exceed 20 billion. These are the numbers that have led ^t^^z&s~!**™a***f**^^ "" liBfruJg^phers, the students of population, to employ such dramatic language as "population explosion."* WORLD POPULATION GROWTH Although the first complete census of mankind has yet to be taken, it is possible to estimate, within reasonable error limits, the population of the world from the end of theJNeoiithicperiod (the new__Stpne_Aga). At that time^jworld population is estimated to have been 10 million. of the Christian era the pojpulation of the world probably numbered between 2l)0"linT31Xr^ era (1650) world popul?tiorrreadTed about 500 million7AT]ft^ej^^ P°PU" lation tota-lfrd-3r5~brllf on: / A' relatively simple analysis of these numbers dis- closes that an enorrnorrs7increase in the speed, or rate, of world population growth has occurred, ejp_ecjanyjduringthe past 3 centuries. Man, or very close kin to manThaTbeen on~tEe~lace ot ffie earth for perhaps 2 to 4 million years. Although it is not known exactly when Homo sapiens, Philip M. Hauser is Professor of Sociology and Director of the Population Research Center, University of Chicago. *Most of the statistics relating to the population of the world are drawn from publications of the United Nations, especially (1, 2). Previous works of the writer have been drawn upon in the preparation of this paper.